Sets the size of the step of muons and charged hadrons to a fixed
fraction of the kinetic energy in different materials
(see also EMFFIX, MULSOPT, STEPSIZE)
WHAT(1) = fraction of the kinetic energy to be lost in a step
(cannot be > 0.2)
Default: if option DEFAULTS is used with SDUM = ICARUS, the
default is 0.02.
With SDUM = HADROTHErapy or PRECISIOn, the default
is 0.05.
If SDUM = CALORIMEtry, the default is 0.08.
With any other SDUM value, or if DEFAULTS is missing,
the default is 0.1.
WHAT(2) = "epsilon" parameter used to check the finite size of the
nucleus when the nuclear form factor is not invoked by
the multiple scattering algorithm (see note below)
For code development only, do not change!
Default = 0.15
WHAT(3) = high-energy limit for the fraction of energy to be lost
in a step (the fraction is given by WHAT(3) times WHAT(1))
For code development only, do not change!
Default = 0.012
WHAT(4) = lower index bound of materials where the specified energy
loss per step is to be applied
(From material WHAT(4)...)
Default = 3
WHAT(5) = upper index bound of materials where the specified energy
loss per step is to be applied
(... to material WHAT(5)...)
Default = WHAT(4)WHAT(6) = step length in assigning indices
(...in steps of WHAT(6))
Default = 1
SDUM : not used
Default (option FLUKAFIX not given): the defaults listed above
apply
Note: Usually there is no need for changing the default value of
10% (0.1) for WHAT(1)
The input value is actually applied as such only at
intermediate energies (between about a few tens of MeV and
1 GeV): at low energies it is slowly increased
to twice the requested value, while at high energies it
decreases to a limit controlled by WHAT(3), usually about one
hundredth of the input value.
The "epsilon" parameter controls the accuracy of the multiple
scattering algorithm by limiting the step. In most cases the
length of the step is practically limited anyway by the hadron
interaction length, so the "epsilon" default value is of little
importance and does not need to be changed.
However, in some problems of large dimensions, especially when
transporting muons, a small value of epsilon can slow down the
calculations without necessity. In such cases, WHAT(2) can be
safely set = 1000.0
Example:
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....
FLUKAFIX 0.03 0. 0. 21. 0. 0.
* The maximum fractional energy loss for hadrons and muons is set to
* 3 percent in material 21.
